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Radial Drilling Mac/line.

The Radial Drilling Machine is most useful fu*
work not readily moved, and has been, since first designed.
in request for holes in steam cylinders or boilers.    The form
depends on the nature of the work, and is sometimes disf
with, and a trolley run' under the drill.    Then the radial ar»
be swung from a wall or roof stanchion.    The machine in 1* * -
has a stationary table, to the top or side of which the \* f
bolted ; and the tool is adjusted over the work (i) by an f* f   *
movement of arm B; (2) a traverse of the saddle c; (3) a *
fall of B.    The last is obtained by turning the spokes K,  **
through worm and wheel, rotate a pinion in rack F ; and i •
first both arm and pillar turn within the bed at x.    The m***
G is driven directly or by back gear, and mitre wheels H H tf *^ '
its motion to the spindle j, from which again the power i*«*  * - -
to the horizontal spindle L by mitre wheels K K.    As arm I -
rise or fall, K is supported by a bearing projecting through    - '*
in the hollow pillar D, and a feather key connects K and j.

The saddle c has bearings M M, and a sleeved mitre w I   *
drives the drill spindle P.    A bearing Q supports a short sj ** '
to which are keyed the mitre wheel R, spur wheel s, and
pulley T, from the last of which various rates of feed are obi ^
as usual; and power is given from L to s by a pinion u, Vh- *
having a feather key, follows the saddle, so as to keep ahv** > *

The drill pSwer passes therefore through five shafts, G, j *   ff
and P, but this is not considered complicated in view ***
advantages obtained.    The saddle is moved along the
turning the hand wheel v, which rotates a small pinion, gearki &
the rack w.   (See also Chap. VII., p. 303 ; and p. 1018.)

Drills.—Some forms are shown at Fig. 169, where A i\   ,#£
pointed and fits in taper hole in the spindle, the cotter a prevc- * v *
slip.    The method of sharpening is seen at b, c, and d, and nt **    **
ee increase endurance of point    B is a pin-drill, where vari;**
in diameter of circle cut is permitted by the movable cti t ?, ** *
wedged in the slot & a hole being first drilled in the wt*r£*
receive pin h.    Cutting angles have been previously discussc** I

The twist drill c, no doubt the very best form for accr*** ^
work, is much in favour.    A socket / fits the spindle, and